Devices, e.g., tablets, smart phones, laptops having a digitizer, etc., are increasingly being used in connection with a pen or stylus (hereinafter these terms are used interchangeably) as an input modality. Certain inputs are possible using a completely passive pen, i.e., where the pen itself is not actively transmitting information but simply serves as an implement to provide contact with a screen—similar to a finger input. Other pens are semi-passive in that they transmit data, e.g., location data, but in a reactive manner, e.g., in response to transmission from a digitizer. Still other pens are so-called “smart pens” that actively transmit input data, e.g., location data, other input data (e.g., button press data, pen status data, etc.) from the smart pen to the device. Smart pens are powered and actively communicate such input data via a low bandwidth pen data channel. Typically each smart pen type uses a proprietary low bandwidth pen data channel.
Active pens increase the signal to noise ratio (SNR) at the sensor/input component by emitting an amplified signal. As a result of the higher SNR, algorithms which detect the pen are able to improve their accuracy and precision. However, the characteristics of the amplified signal are specific to a given pen vendor and will degrade performance if the pen is used on a system or device from another vendor. It is not possible to use the same active pen on systems or devices from different vendors.